ICIITHYOCRINIDAE 337 



AMPHICRINUS Springer 

 Plates XL, figs, p-ii; LX, figs. 12a, b 



Amphicrinus Springer, Jour. Geology, XIV, 1906, p. 518; (Springer MS.), Wright, Trans. Edinburgh 

 Geol. Soc, X, pt. 2, 1914, p. 161. — Zittel-Eastman, Textbook Paleontology, 1913, p. 205. 



Fig. 45. Amphicrinus 



Ichthyocrinidae with rays above radials partly separated by solid plates, 

 arched over by brachials. Crown ovoid to subglobose, expanding from radials 

 up. Infrabasals entirely within the ring of basals, sometimes resorbed. No 

 radianal. Anal x followed by others in a single row. Interbrachials numerous, 

 in more than one row. Primibrachs two. Arms isotomous, interlocking. 

 Column large, covering infrabasals and part or all of basals. 



Genotype. Amphicrinus scoticus Springer. 



Distribution. Upper part of Lower Carboniferous to Lower Coal Meas- 

 ures ; Scotland and the United States. The latest known genus. 



This genus was proposed by me to receive certain specimens from the British Carbonifer- 

 ous which could not be placed under any other genus previously described. It bears a general 

 resemblance to the Forbesiocrinus type, having the anal and interbrachial areas filled with 

 solid plates, although differing in the complete arching over of these plates by the abutting 

 rays and their lower divisions ; but it is remarkable for having, contrary to the rule in the 

 crinoids generally, the anal interradius smaller than those of the regular areas — a character 

 which distinguishes it readily from all other of this family. In the type and only well-known 

 species each regular interradius has two vertical columns of large plates resting upon the 

 first interbrachial, and extending for five or six ranges ; while the anal interradius has but a 

 single series of such plates. Its family position is determined by the remarkably small size 

 of the basal circlet, which is usually much less than that of the column facet, and by the 

 tendency to resorption and sometimes to complete disappearance of the infrabasals. 



In the latter respect it exhibits the tendency of the family to the fullest extreme. Figure 

 10 of Plate XL shows the infrabasals partially resorbed, fitting accurately within the ring 



